This invention relates broadly to conveyor construction and, more particularly, pertains to developments in the mechanism for tensioning the continuous belt of the conveyor.
The present invention contemplates improvements to a known conveyor construction such as generally disclosed in Hosch et al. U.S. Pat. No. 6,298,981, the disclosure which is hereby incorporated by reference. The ""981 patent discloses a conveyor construction including a frame and a tensioning section including spaced side members mounted for longitudinal movement relative to the frame. The tensioning section includes a spindle about which a conveyor belt is trained, and movement of the tensioning section functions to control the tension of the belt. A drive and locking arrangement for imparting movement to the tensioning section and for selectively locking the tensioning section in position includes a pair of pinion carriers or retainer blocks mounted one to each side of the frame, with a drive pinion being rotatably supported by the retainer blocks. Each side member includes integrally formed gear teeth engageable with opposite ends of the drive pinion, and a drive pinion actuator is engaged with one side of the frame for imparting rotation to the drive pinion to extend and retract the tensioning section. A locking arrangement is interconnected with the opposite end of the drive pinion, and functions to selectively frictionally engage the drive pinion with one of the retainer blocks to prevent rotation of the drive pinion and to thereby maintain the tensioning section in a desired position relative to the frame.
This construction is generally satisfactory, but can present problems upon the imposition of a sudden or random force applied to the spindle once the tensioning section has been locked into a particular position so as to set a desired tension for the moving belt. Such a force may be caused by a collision or impact of the spindle with another piece of equipment or with a structural member, such as a wall. If this impact force has enough intensity, it can overcome the frictional locking force of the locking arrangement, such as by shearing or stripping the locking components, resulting in undesirable, retractable movement of the tensioning section which will alter the belt tension and negatively affect the performance of the conveyor. In some designs, the impact force may act to drive the gear teeth on the moving side members against the drive pinion as its locked position is overcome causing damage or destruction to the gear teeth on the drive pinion.
It is desirable to provide a conveyor construction which rectifies the problems described above, and offers enhancements in the components, assembly, operation and maintenance of the tensioning section of the conveyor.
It is one object of the present invention to provide a conveyor construction in which involuntary, retractable movement of the tensioning section is limited so as to maintain a desired tension on the conveyor belt and preserve the integrity of the drive pinion structure.
It is also an object of the present invention to provide a conveyor construction which relies upon wedging action between the components of the tensioning unit to prevent damage to the drive pinion structure when an undesirable force is inflicted upon the spindle.
It is a further object of the present invention to provide a conveyor construction having an improved structure for engaging the drive pinion structure with the tensioning section.
In accordance with one aspect of the invention, a conveyor construction includes a frame having a pair of side members, a belt and a tensioning section mounted for longitudinal extendable and retractable movement relative to the frame for establishing a desired tension on the belt. The tensioning section includes a spindle engaged with the belt and a pair of side plate structures connected to the spindle and located one adjacent each frame side member. A drive member is rotatably mounted relative to the frame and is drivingly engaged with the tensioning section for imparting longitudinal extendable and retractable movement relative to the frame upon rotation of the drive member. A locking device exerts a frictional locking force on the side plate structures relative to the frame side members for selectively fixing the position of the tensioning section relative to the frame. This aspect of the invention contemplates an improvement in the form of a restraining arrangement incorporated in the side plate structures for limiting the retractable movement of the tensioning section upon the imposition of a random force applied to the spindle and overcoming the frictional locking force of the locking device so as to substantially retain the desired tension on the belt and preserve operability of the drive member.
Each of the side plate structures includes a first member which is selectively moveable or lockable relative to a fixed second member. The first member preferably includes a head plate extending longitudinally along an inside surface of one of the frame side members. The second member preferably includes a clamp plate extending longitudinally along an inside surface of the head plate. The head plate is integrally constructed of a forward portion, a mid portion and a rear portion. The spindle has opposed ends, each end being rotatably mounted to the head plate. The forward portion of the head plate includes a circular socket member connected to the mid portion by an angularly and inwardly offset segment. The socket member receives a spherical ball bearing assembly for enabling rotation of the spindle. The mid portion is formed with a first throughslot and includes a first pair of upper and lower angled surfaces. The rear portion is formed with a second throughslot and includes a set of teeth extending axially along a wall forming the second throughslot. The drive member has opposed ends provided with drive pinion ends rotatably mounted to the frame members. Each drive pinion end extends into the second throughslot for engagement with axially extending teeth on the rear portion of the head plate. The clamp plate includes a restraining block integrally connected to an extension portion which rotatably receives an adapter connected to each drive pinion end. The restraining block is inserted into the first throughslot formed in the mid portion of the head plate and locked to one of the frame side members. The restraining block includes a second pair of upper and lower angled surfaces which are selectively slidably and lockingly engageable with the first pair of upper and lower angled surfaces on the mid portion of the head plate. The first and second pairs of angled surfaces are constructed and arranged to move into a wedging relationship with one another upon imposition of the random force applied to the spindle.
In accordance with another aspect of the invention, a conveyor construction includes a frame having a pair of side members, a belt and a tensioning section mounted for longitudinal extendable and retractable movement relative to the frame for establishing a desired tension on the belt. The tensioning section includes a spindle engaged with the belt and a pair of side plate structures connected to the spindle and located one adjacent each frame side member. A drive member is rotatably mounted relative to the frame and is drivingly engaged with the tensioning section for imparting longitudinal extendable and retractable movement relative to the frame upon rotation of the drive member. A locking device exerts a frictional locking force on the side plate structures relative to the frame side members for selectively fixing the position of the tensioning section relative to the frame. The conveyor construction is improved wherein each of the side plate structures includes a first member selectively movable and lockable with respect to a second member. The first member is freely slidable upon the second member when the tensioning section is extended, and the first member is slidable into a wedging relationship with the second member when the tensioning section is retracted.
The first member is preferably a head plate formed with a top wall, a bottom wall and a first throughslot. The head plate includes upper and lower inner edges having planar surfaces which angle slightly outwardly towards a respective one of the frame side members as the head plate extends from front to rear. The second member is preferably a clamp plate including a restraining block having an outer section received in the first throughslot, and an inner section which is coplanar with an extension portion. The outer section of the restraining block includes an upper horizontal surface engageable with an outer, bottom portion of the head plate top wall, and a lower horizontal surface engageable with an outer, top portion of the head plate bottom wall. The inner section of the restraining block includes an upper vertical face engageable with the upper inner edge of the head plate, and a lower vertical face engageable with the lower, inner edge of the head plate. The upper and lower vertical faces have planar surfaces which extend at an angle from front to rear similar to the angle formed on the upper and lower inner edges on the head plate. The locking device includes a pair of fasteners passing through respective holes formed in a respective frame side member and the first throughslot for threaded engagement with the restraining block whereby tightening of the fasteners will lock the head plate and clamp plate together relative to the respective frame side member.